Abstract
Deep rolling is an industrially widely established mechanical surface treatment process for the modification of roughness and fatigue resistance. However, the process has not been considered as a potential method for the mechanical post welded treatment of welded joints yet. Even, the potential of deep rolling for increasing the fatigue strength is comparably well-known in the case of non-welded components. Therefore, the effect of deep rolling (hydrostatic mounted tool) and diamond burnishing (mechanical mounted tool) to increase the fatigue strength of butt joints was approved in this work for aluminium alloy AlMg4,5Mn0,7 (EN AW 5083). For this purpose, fatigue tests under full tensile loading were performed in as-welded and deep rolled, burnished and ultrasonic impact treated conditions. Different residual stress states as well as work hardening states are determined in deep rolled and burnished condition. However, similar and significant fatigue life improvement was determined for both processes.
Highlights
The fatigue resistance of steel and aluminium welded joints is lower compared to the base material
These investigations show that the work hardening can inhibit or retard surface fatigue crack initiation as well as fatigue crack growth under condition that the near-surface work hardening state is stable during cyclic loading
As a reason of comparable low contact force, compared to highfrequency mechanical impact treatment, of less than 380 N, the investigations are limited to butt joints made of EN AW 5083 with a comparable low yield strength of 203 MPa
Summary
The fatigue resistance of steel and aluminium welded joints is lower compared to the base material. Multiple methods for the post weld treatment have been developed and approved in the last decades with the aim of increasing the fatigue resistance of welded joints, for example, the high-frequency mechanical impact (HFMI) treatment [1]. Deep rolling and burnishing are a widely industrially applied mechanical surface treatment process with a high degree of automatisation for the modification of hardness, roughness and residual stress state as well as for the structuring of surfaces. The aim of the present work was to investigate the possibility of fatigue strength improvement by deep rolling and burnishing process of welded aluminium alloys in larger scales compared to the low-scale specimens in the previous study [16].
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